Strange twisted bone with Copy Rotation
There are a few things you can do. First would be to adjust the "Roll" of bones in edit mode, then they will have the same starting rotation. You can also restrict rotation on the axis of weird twisting or in Copy Rotation Constraint properties set copy only to those axis that work properly, or if the rotation of bones on the twisting axis is exactly opposite, select Invert in Copy Rotation Constraint properties for this axis, but if you want to have easy life with the rig, use the first option.